This invention relates to a control valve and more particularly to a control valve having a bypass valve for bypassing load generated pressurized fluid around a valve spool.
In many hydraulic systems, one or more hydraulic jacks are employed to raise and lower a heavy load. Such heavy loads generate high fluid pressure in the hydraulic jacks. When the control valve is shifted to lower the load, the pressurized fluid exhausted from the jack passing through the control valve generates high flow forces on the valve spool. The high flow forces are particularly troublesome when the operator is modulating the valve to control the rate of lowering. In some cases, the flow forces can impair the operator's capability of modulating the fluid flow exhausted from the hydraulic jacks.
One solution to the problem of metering fluid exhausted from a hydraulic jack employs a check valve and a fluid discharge valve for passing the exhausted fluid directly to a drain port thereby bypassing the main valve spool. However, that valve arrangement employs a second valve spool positioned remote from the main valve spool for controlling the opening of the fluid discharge valve. The addition of a second valve spool for controlling the discharge valve not only adds cost to the manufacturing of the valve arrangement, but also adds to the complexity of the valve arrangement since other controls must be provided to coordinate the movement of the main valve spool and the second valve spool.